O'Brien first played hurling and Gaelic football at club level with Geraldine O’Hanrahans. He had his first success in 1957 when the club beat Shemaliers by 6-07 to 5-06 to win the Wexford IHC title.[1] He added a Wexford JFC medal to his collection in 1963 after a defeat of Kilanerin in the final. O'Brien won a Wexford SHC medal in 1966, following Geraldine O'Hanrahans 2-10 to 3-o4 win over Enniscorthy Shamrocks in a final replay.[2]
At inter-county level, O'Brien first played for Wexford as a member of the minor team. He progressed to the junior team and won a Leinster JHC title in 1957. O'Brien made his senior team debut during Wexford's National Hurling League-winning campaign in January 1957, however, it took a few years for him to become a regular member of the team.
O'Brien won his first Leinster SHC medal in 1960 and was at wing-forward for the 2-15 to 0-11 defeat of Tipperary in the 1960 All-Ireland final.[3] He collected further Leinster SHC honours in 1962 and 1965, however, Wexford had subsequent All-Ireland final defeats by Tipperary on both occasions.[4] O'Brien captained Wexford to the National Hurling League title in 1967.[5] He collected a fourth and final Leinster SHC medal in 1968 before later claiming a second All-Ireland SHC medal after lining out in the 5-08 to 3-12 victory over Tipperary in the 1968 All-Ireland final.[6]
Performances at inter-county level for Wexford resulted in O'Brien being called up to the Leinster inter-provincial team. He won his sole Railway Cup medal in 1965 following a defeat of Munster in the final.[7]